Of all the fertility questions we are asked, IUI comes up most often. It is the simplest form of assisted conception, far less expensive than IVF, and widely available in Sri Lanka. But it only works well for the right couples — and much disappointment comes from IUI being used when it was never likely to help. This article explains what IUI is, who it suits, what a cycle involves and what success realistically looks like.

What is IUI?

Intrauterine insemination means placing a prepared sample of sperm directly into the womb, through the cervix, around the time of ovulation. The sperm are "washed" in the laboratory so that the most motile ones are concentrated into a small volume. The idea is simple: more good sperm, closer to the egg, at exactly the right time. Fertilisation still happens naturally inside the fallopian tube — unlike IVF, where eggs and sperm meet in the laboratory.

Who is IUI suitable for?

IUI needs three things to be true: at least one open fallopian tube, an adequate number of moving sperm, and ovulation that is either happening or can be stimulated. Given those, it is most useful for:

  • Unexplained infertility — all tests normal, but no pregnancy after a year or more of trying
  • Mild male factor — slightly low sperm count or motility (see our guide to male factor infertility)
  • Ovulation problems such as PCOS, combined with ovulation induction
  • Cervical factor or difficulty with intercourse, including vaginismus
  • Mild endometriosis with open tubes

IUI is not appropriate when both tubes are blocked, when sperm numbers are very low, in moderate-to-severe endometriosis, or where the woman's age and egg reserve mean that time matters more than cost. In those situations IVF is the better first step, and offering IUI only delays it.

Before you start: the essential checks

A tubal test is essential — IUI into a womb whose tubes are blocked cannot work. In Sri Lanka this is most often done by laparoscopy and dye test or by HSG (an X-ray dye test). A recent semen analysis, confirmation of ovulation and a baseline scan complete the work-up. Both partners should also have had their general preconception checks.

What happens in an IUI cycle

  1. Stimulation (usually). Most IUI cycles use letrozole or clomifene tablets, sometimes low-dose hormone injections, from the early days of the cycle to grow one or two follicles. Natural-cycle IUI without medication is an option for some couples.
  2. Monitoring. A transvaginal scan from around day 10–12 measures the follicles and the womb lining. The aim is one, at most two, mature follicles — more than that and the cycle is usually cancelled because of the risk of multiple pregnancy.
  3. Trigger. When the lead follicle reaches about 18 mm an hCG injection triggers ovulation, which follows roughly 36 hours later.
  4. Sperm preparation. On the day, the partner produces a sample, which is washed and concentrated in the laboratory over one to two hours.
  5. Insemination. A fine soft catheter is passed through the cervix and the sample is placed in the womb. It takes a few minutes, feels similar to a smear test and needs no anaesthetic. You can return to normal activity the same day — lying down afterwards makes no difference to the result.
  6. The two-week wait. Some doctors prescribe progesterone support. A pregnancy test is done about 14 days later.

How successful is IUI?

Honesty matters here. A single stimulated IUI cycle gives a pregnancy in roughly 10–15% of couples under 35, falling to under 5% per cycle after 40. These figures are much lower than IVF, but the treatment is far less invasive and far cheaper, so over three or four cycles the cumulative chance becomes worthwhile for suitable couples. Most pregnancies from IUI happen within the first three to four attempts; continuing beyond that rarely adds much, and it is usually time to discuss IVF.

Success depends above all on the woman's age, the reason for infertility, the number of motile sperm after washing, and whether a mature follicle was present at the right time. If you want to see where IUI sits in the overall plan for your situation, our fertility pathway tool walks through the usual sequence.

Why IUI cycles fail

  • The egg itself was not healthy — the commonest reason, and increasingly so with age
  • Timing — insemination too early or too late relative to ovulation
  • Tubal disease that was not fully appreciated, or a hydrosalpinx (a fluid-filled tube) that leaks back into the womb
  • Sperm quality lower than the raw count suggested
  • Undiagnosed endometriosis or a womb problem such as a polyp or fibroid in the cavity

None of these mean you did something wrong. But after two or three unsuccessful cycles it is worth a proper review rather than simply repeating the same treatment.

Risks and side effects

IUI itself is very safe; mild cramping or spotting for a day is common and infection is rare. The real risk comes from the stimulation: multiple pregnancy. Twins and triplets carry much higher risks for mother and babies, which is why careful scan monitoring and a willingness to cancel over-responding cycles are not optional extras. Ovarian hyperstimulation syndrome is uncommon with tablets but possible with injections — severe abdominal pain, bloating, vomiting or breathlessness should be reported at once.

The bottom line

  • IUI places washed sperm into the womb at ovulation; fertilisation still happens naturally in the tube.
  • It suits unexplained infertility, mild male factor and ovulation problems — only with at least one open tube and adequate sperm.
  • Expect 10–15% per cycle under 35; most successes come within three to four cycles.
  • Scan monitoring is essential to avoid multiple pregnancy.
  • If three or four good cycles have failed, or your age and reserve argue for speed, IVF is the next step — not more IUI.

If you would like a frank assessment of whether IUI is the right step for you, you can consult us at Sugabi Clinic Ragama or book a video consultation.

References

  1. National Institute for Health and Care Excellence. Fertility problems: assessment and treatment (CG156) [Internet]. London: NICE; 2013 [updated 2017 Sep 6; cited 2026 Oct 5]. Available from: nice.org.uk/guidance/cg156
  2. Human Fertilisation and Embryology Authority. Intrauterine insemination (IUI) [Internet]. London: HFEA; [cited 2026 Oct 5]. Available from: hfea.gov.uk
  3. NHS. Infertility — treatment [Internet]. London: NHS; [cited 2026 Oct 5]. Available from: nhs.uk
  4. Cohlen B, Bijkerk A, Van der Poel S, Ombelet W. IUI: review and systematic assessment of the evidence that supports global recommendations. Hum Reprod Update. 2018;24(3):300–19. doi:10.1093/humupd/dmx041
  5. Farquhar CM, Liu E, Armstrong S, Arroll N, Lensen S, Brown J. Intrauterine insemination with ovarian stimulation versus expectant management for unexplained infertility (TUI): a pragmatic, open-label, randomised, controlled, two-centre trial. Lancet. 2018;391(10119):441–50. doi:10.1016/S0140-6736(17)32406-6
  6. Ayeleke RO, Asseler JD, Cohlen BJ, Veltman-Verhulst SM. Intra-uterine insemination for unexplained subfertility. Cochrane Database Syst Rev. 2020;(3):CD001838. doi:10.1002/14651858.CD001838.pub6
  7. European Society of Human Reproduction and Embryology. Unexplained infertility: guideline of the ESHRE [Internet]. Strombeek-Bever: ESHRE; 2023 [cited 2026 Oct 5]. Available from: eshre.eu